@mixin gradient($start-color, $end-color, $orientation: horizontal) {
  background: $start-color;

  @if $orientation == 'vertical' {
    background: linear-gradient(to bottom, $start-color, $end-color);
  } @else if $orientation == 'horizontal' {
    background: linear-gradient(to right, $start-color, $end-color);
  } @else {
    background: radial-gradient(ellipse at center, $start-color, $end-color);
  }
}
